As most of you know, Five Nights at Freddy's 3 features several minigames, each featuring a specific animatronic.
One of these includes Stage01, in which you control a yellow bear through nine identical frames (organized like a numeric keypad).
First of all, just to cover the groundwork, the animitronic is Golden Freddy. I know this is obvious for most, but I should briefly go over the evidence anyway. One, the bear is yellow. Two, the bear glitches through walls and the ground, something that has been attributed to Golden Freddy in FNAF1. Three, all of the other minigames feature animitronics outside of the original four.
The second thing I want to point out is that it is commonly believed the yellow bunny standing next to him is Springtrap, which would be logical as they are both yellowish animitronics; animitronics that were both neglected and disused; and animitronics that look or function vaguely like suits.
From the information we recieve about Stage01, we can also assume the minigame occurs during the life of the original restraunt: Fredbear's Family Diner. This can be assumed because one, there are only a small number of animitronics (two). Second, those two animitronics are Golden Freddy and Springtrap, the former only believed to have been in use in Fredbear's Family Diner. Thirdly, the minigame appears to take place in a very small restraunt, Fredbear's Family Diner assumed to be the smallest one.
The reason the approximate time Stage01 takes place is important is because of the following: The FNAF3 Minigames feature animitronics meeting the spirits of dead children, and then giving them cake. Assuming Stage01 takes place before any of the games, then that would mean there was a dead child prior to the Crying Child (assumed to be The Puppet) from Take Cake to the Children. As the minigames are telling the tales of the animitronics fusing with the spirits of dead children, this would mean that Golden Freddy existed before The Puppet.
This is even more significant because of the Death Minigame Give Gifts Give Life in FNAF2. At the end of the Minigame, for a single frame, a fifth spirit is shown amongst the main four. Most assume that this fifth spirit is Golden Freddy, however, if Golden Freddy's spirit predates The Puppet's, then this is impossible.
The question arises, who is the fifth child???